John Gill Commentary 1 Kings 1:36

"And Benaiah the son of Jehoiada answered the king, and said, Amen: Jehovah, the God of my lord the king, say so [too]." — 1 Kings 1:36 (ASV)

And Benaiah the son of Jehoiada answered the king
In the name of the rest:

and said, Amen ;
they all assented to it, and expressed their satisfaction in it:

the Lord God of my lord the king say so [too] ;
let it appear, by the prosperity and success that shall by divine Providence attend the new king, that this is according to the will of God.